Abstract: In view of the poor degradability of polyvinyl alcohol (PVA) desizing wastewater during the preparation of microfiber synthetic leather, and serious environmental pollution, PVA, water-soluble polyester (WSPET), sodium carboxymethyl cellulose (CMC), sodium alginate (SA), and white sugar (WS) were used for sizing the island-in-sea microfiber nonwoven fabric, and impregnated with water-based polyurethane (WPU) to make microfiber synthetic leather. The effects of different size mixtures on the properties of microfiber leather were investigated. The results indicated that the sizing treatment can improve the air permeability, moisture permeability, softness and mechanical properties of the microfiber synthetic leather, and the water vapor permeability, air permeability and softness were increased by 123.5, 184.7 and 37.7%, respectively. The microfiber synthetic leathers treated by PVA, WSPET and CMC sizing exhibited similar water vapor permeability, air permeability and softness. While, the microfiber synthetic leathers treated by SA and WS sizing had poor water vapor permeability, air permeability and softness. Through comprehensive analysis of performance, WSPET, CMC can be used as an economical, environmentally friendly and sustainable size mixture for the preparation of microfiber synthetic leather.